In the field of electrophotographic color printing wherein cyan, yellow, magenta, and black color toners are developed in sequence and serially applied to the surface of a print medium, certain known color image development processes have required that separate photoconductive drums be used in the development of each of the cyan, yellow, magenta, and black color images. An example of a linear laser color printing system wherein cyan, magenta, yellow, and black colors are applied in series to a print medium, such as paper, and there superimposed as C, M, Y, and K color images on top of one another is disclosed in U.S. Pat. No. 4,660,077 issued to Kawamura et al and assigned to Canon of Japan and incorporated herein by reference.
One disadvantage of the process and system disclosed in the above Kawamura et al patent is that this approach to color printing uses separate photoconductive drums for each of the C, M, Y, and K primary colors. These individual drums are positioned in a line adjacent to one another and located immediately adjacent to the transfer medium. Thus, this color printer arrangement requires that these individual photoconductive drums be precisely aligned with respect with each other in order to ensure good image matching, good color resolution and print quality of the reproduced color image. In addition, the approach in Kawamura et aI U.S. Pat. No. 4,660,077 requires that the photoconductive drums used therein be precisely and exactly sized and shaped in order to further assure a precise multiple color image alignment and pattern replication and an exact positioning of the C, Y, M, and K primary colors on top of one another to form the composite multi-color image on the print medium.
Another type of laser color printer and copier of the prior art which uses a single photoconductive drum for image reproduction purposes has been designed to use a rotating drum on which the print medium is wrapped during the printing process. The requirement for such a system carries with it a number of attendant disadvantages such as additional cost, lack of reliability, and maintenance. One such copier which is generally well known in the art and which uses such a rotating drum is the Canon Laser Copier 200 or the "CLC 200".